Group 1 beta-expansin (EXPB1)

Group 1 beta-expansin refers to a subfamily of expansin proteins, primarily found in grass pollen, with Zea m 1 (encoded by the EXPB1 gene in maize) being a well-studied example. Beta-expansins are non-enzymatic, extracellular proteins involved in plant cell wall modification: they induce wall loosening, cell stress relaxation, and irreversible wall extension without catalyzing the hydrolytic breakdown of cell wall polysaccharides. Their action is thought to involve binding to hemicellulosic polysaccharides (especially glucuronoarabinoxylan) and facilitating the noncovalent rearrangement of the cell wall matrix. Group 1 beta-expansins in grass pollen function as major allergens, responsible for most IgE cross-reactivity and clinical allergy symptoms associated with grass pollen exposure in humans. Structurally, beta-expansins (such as EXPB1) contain two domains: domain 1 has similarity to glycoside hydrolase family 45 but lacks enzymatic activity, while domain 2 adopts an immunoglobulin-like fold. Beta-expansins are not considered classical therapeutic targets (e.g., not a druggable enzyme or receptor) but are of medical and biotechnological interest due to their allergenicity and role in plant development.

Other names

Group-1 grass pollen allergenZea m 1 (in maize)β-expansinbeta-expansinEXPB1pollen allergen group 1